Rates of obesity and overweight in the U.S. are increasing rapidly, while current weight control programs remain relatively ineffective. A primary' prevention approach, which targets individuals at risk for weight gain, may prove more efficacious. Such prevention programs should include assessment of long-term outcome and, to maximize participation rates, should be tailored to appeal to the at-risk population. The aim of the present study is, therefore, to test the long-term efficacy of two programs for primary prevention of weight gain in normal-weight women aged 25-34, a group at high risk for weight gain, and to assess participation rates in these two treatment formats. Subjects (N=300) responding to recruitment materials will be randomly assigned to 1 of 3 treatment formats (group meetings designed to appeal to women aged 25- 34, correspondence course, no-treatment control). Subjects in the group meeting format and the correspondence course will participate in 24- month behavioral weight gain prevention programs. For all three formats, weight will be assessed at 0, 12, 24 and 36 months. Participation rates for the two active treatments will be assessed at 12 and 24 months. Primary' outcome variables will be the proportions of subjects in each format maintaining baseline weight at 36 months and participation rates for the two active treatments at 12 and 24 months. The proposed research is important because it explicitly focuses on primary prevention of weight gain in individuals at risk for future weight gain. It seeks to determine the long-term efficacy of two such programs and to determine the treatment format which produces the largest participation rates. If efficacious, the interventions can be adapted for use in clinical settings. Determination of participation rates can also be used to increase the population outreach of weight gain prevention programs.